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Old 12-12-2008, 05:24 AM   #1
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Default Anyone heard of pinching cylinders

Kind of new to nitro and bought a used rustler with a .15 pro. I assume it has weak compression. (hard to start, dies easily). piston and sleeve not too expensive. But i heard about a sleeve pincher. Some racers i know pinch before a race. Good idea??? I can get an entire new engine for around 90.00. any help would be appreciated. P.S i know your gonna say put the 2.5 or 3.3 but i tell ya this thing rips and is easy to control.
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Old 12-12-2008, 05:34 AM   #2
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you will have better luck with a new engine, the pincher could work but if the engine has had dirt or somthing in it, it wont help, the 2.5 is a .15 the 3.3 is a .18
but to awnser you question, pinching is a common practice, the pincher only works if there are no scratches on the sleve and piston, then you may be able to extend the life of the engine a little.
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Old 12-12-2008, 06:35 AM   #3
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Having a piston sleeve pinched is somewhat common. The cost is normally $15 to $35 depending on the process and pincher. There are cheap pinchers on ebay and units that cost $800 or more. The more expensive units can take a motor back to original specs.

What racers call a fresh pinch is having a motor repinched before it actually losses performance. This keeps the motor in top running shape and extends the life. Waiting till a motor has has lost most or all of its compression will only extend the life for an uncertain amount of time.
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Old 12-12-2008, 12:25 PM   #4
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Having a piston sleeve pinched is somewhat common. The cost is normally $15 to $35 depending on the process and pincher. There are cheap pinchers on ebay and units that cost $800 or more. The more expensive units can take a motor back to original specs.

What racers call a fresh pinch is having a motor repinched before it actually losses performance. This keeps the motor in top running shape and extends the life. Waiting till a motor has has lost most or all of its compression will only extend the life for an uncertain amount of time.
I know of a couple of different ways to tell if the piston/sleeve is very worn. How do you determine if it's "mostly" worn and should be pinched to avoid running it until the very end?
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Old 12-12-2008, 12:38 PM   #5
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I know of a couple of different ways to tell if the piston/sleeve is very worn. How do you determine if it's "mostly" worn and should be pinched to avoid running it until the very end?
i have been told a couple ways......one way is to hold the engine up by the crank and the compression should hold up the engine for 10 seconds......also i was told to look in the exaust port and watch the piston, turn the crank over and it should feel spongy or start to make compression before the top of the wrist pin gets to the top of the exaust port.......the first one i read on the net, the second one was told to me by Ed Bridges himself. Ed also said the 10 second rule is a pretty good way of getting an idea for your engine wear.......

on a side not that same race day i spoke with him about pinching a engine, he laughed and said "i got a pair of vice grips over here i can pinch it for you" and laughed like it really dont work well.....im shure there are ppl. who will dispute that but that is just one opinion from somebody who knows a lot more than i do when it comes to nitro engines.
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Old 12-12-2008, 01:29 PM   #6
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i have been told a couple ways......one way is to hold the engine up by the crank and the compression should hold up the engine for 10 seconds......also i was told to look in the exaust port and watch the piston, turn the crank over and it should feel spongy or start to make compression before the top of the wrist pin gets to the top of the exaust port.......the first one i read on the net, the second one was told to me by Ed Bridges himself. Ed also said the 10 second rule is a pretty good way of getting an idea for your engine wear.......

on a side not that same race day i spoke with him about pinching a engine, he laughed and said "i got a pair of vice grips over here i can pinch it for you" and laughed like it really dont work well.....im shure there are ppl. who will dispute that but that is just one opinion from somebody who knows a lot more than i do when it comes to nitro engines.
I recently heard about the 10 second test. Up until now I always ran them until they wouldn't stay running, pull the piston/sleeve and find out for sure that they were done for The see how far the piston will push through the sleeve test.

I'll keep these two tests in mind to try and take care of my new engine better. I have had one sleeve pinched and it worked OK but the sleeve wouldn't easily go back into the engine That can't be good. I'd try it again though. $20 vs. $100 is worth the chance that it works out instead of buying new.
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Old 12-12-2008, 01:49 PM   #7
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When I first heard about pinching I had a picture in my head of some guy squeezing a sleeve in a vise. Pinching may not be the best term, it is more of a resizing. Basically you put force on the outside of the sleeve and make the sleeve tighter at the top, but evenly all the way around to keep it round. I personally would rather run a motor that has been pinched vs. a new piston and sleeve. The motors I pinch I only run 2 tanks just a couple hours richer and go race. New p/s you have to rebreak in and get them loosened up again before they perform well.
As someone else stated the rest of the motor has to be in good condition also or it may not be worth it.
I charge $15.00 to pinch a piston and sleeve or $35.00 if you send the whole motor. When I rebuild the motor I clean, inspect, pinch, replace bearings etc. (parts not included) You do not pay if the motor is not fixable or not worth it.

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Old 12-12-2008, 02:01 PM   #8
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I got a couple of mine done by OS Rocket www.osrocketracing.com

Worked out really well, did my Sirio last year and it actually ran better. Longer run times (12min) and it lasted another 4 gallons before I sold it.

Depending how worn out your engine is I would request a 'light' pinch as the first one I did was so tight that I had a really hard time re-breakin it in.

Also, like mentioned here, make sure your P/S are in decent condition and not contaminated.
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Old 12-12-2008, 03:58 PM   #9
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I've heard Os Rocket does them pretty tight. I just don't see a need to go real tight if you keep the sleeve really round. My goal is to get it about like it was when it had a gallon on it, that's when they start to run the best.

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Old 12-12-2008, 05:28 PM   #10
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Default thanx 4 the info on pinching

Again all my questions answered in detail. thank you all for your replies. what a great forum. "Baustin" what is the 10 second rule on engine wear in detail.
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Old 12-12-2008, 07:38 PM   #11
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I recently heard about the 10 second test. Up until now I always ran them until they wouldn't stay running, pull the piston/sleeve and find out for sure that they were done for The see how far the piston will push through the sleeve test.

I'll keep these two tests in mind to try and take care of my new engine better. I have had one sleeve pinched and it worked OK but the sleeve wouldn't easily go back into the engine That can't be good. I'd try it again though. $20 vs. $100 is worth the chance that it works out instead of buying new.
I have a test that I've used over the years. When the crank can be turned over TDC with little resistance w/ the plug removed, I'll add a drop or two of after-run oil and reinstall the plug. Then I'll turn the crank over by hand all the way up and past TDC but not far enough to expose the exhaust port. I'll rock the crank back and forth from 10 o'clock to 2 o'clock and back for a total of 10 compressions. If I can still feel pressure as I pass TDC @ compression 6 or higher; I judge the P/S fit to still be good. If compression is lost by 4 or less the fit needs to be corrected. If I can only get 1 or 2 cycles in, I call it DOA and replace the P&S.

by the way I do this test on a cold engine.

but... we each have our own ways to judge what is good and bad.

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Old 12-12-2008, 09:17 PM   #12
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I would pinch the whole motor, what are you going to do with just the sleeve.
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Old 12-13-2008, 08:16 AM   #13
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Quote:
Originally Posted by bjr48 View Post
I know of a couple of different ways to tell if the piston/sleeve is very worn. How do you determine if it's "mostly" worn and should be pinched to avoid running it until the very end?
I use several methods. First off, I pay attention to how easily the motor spins over on the starter box. Then, about once a race day, I try turning the motor over in the car after it is hot. You will soon get a feel for compression on a hot motor.

Each brand of motor will have a different amount of pinch. For example, older OS and Nova-based motors have a lot of pinch. V-spec and Sportwerks motors run well with minimal pinch.

The ten-second test is a good one to use when the motor is out for servicing the clutch. The last test I do is to push the piston up into the sleeve before getting it re-sized.
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